The present invention relates to method for producing a vane for application in a component in a gas turbine engine, especially a jet engine. The vane is especially suited for application in a stator component and primarily in an intermediate case (IMC) in an aircraft engine of the turbofan type. The invention is further directed to such a vane per se and a stator component (IMC) comprising the vane.
An aircraft gas turbine engine of the turbofan type generally comprises a forward fan and booster compressor, a middle core engine, and an aft low pressure power turbine. The core engine comprises a high pressure compressor, a combustor and a high pressure turbine in a serial relationship. The high pressure compressor and high pressure turbine of the core engine are interconnected by a high pressure shaft. The high-pressure compressor, turbine and shaft essentially form a high pressure rotor. The high-pressure compressor is rotationally driven to compress air entering the core engine to a relatively high pressure. This high pressure air is then mixed with fuel in the combustor and ignited to form a high energy gas stream. The gas stream flows aft and passes through the high-pressure turbine, rotationally driving it and the high pressure shaft which, in turn, rotationally drives the high pressure compressor.
The gas stream leaving the high pressure turbine is expanded through a second or low pressure turbine. The low pressure turbine rotationally drives the fan and booster compressor via a low pressure shaft, all of which form the low pressure rotor. The low pressure shaft extends through the high pressure rotor. Most of the thrust produced is generated by the fan.
Part of the incoming air flow to the aircraft engine enters an inner, primary gas duct, which guides the air to the combustor, and part of the incoming air flow enters an outer, secondary gas duct (fan duct) in which the engine bypass air flows.
The intermediate case (IMC) is a non-rotating component and forms a load-carrying structure. In a commercial, 2-shaft turbofan engine, the intermediate case is located between the Low Pressure Compressor and the High Pressure Compressor in the engine axial direction. At this location, the operating temperature is considered to be relatively low compared to the components downstream of the combustion chamber and is therefore referred to as a cold structure.
The intermediate case comprises a core structure, which comprises the primary gas duct, and a by-pass structure, which comprises the fan duct. The present invention is especially suited for the by-pass structure. The by-pass structure comprises an inner ring, an outer ring and a plurality of circumferentially spaced vanes arranged between the inner ring and the outer ring, wherein gas flow channels are formed between the adjacent vanes. The circumferentially spaced vanes are often called Outlet Guide Vanes (OGV).
The intermediate case has a number of various functions. The engine mount, i.e the connection between the engine and the aircraft, is placed on the outside of the IMC. The IMC is thereby exposed to high loads. The IMC is also a support for the bearings on the low pressure shaft and the high pressure rotor. Transmission of power between gearboxes may also be led through the intermediate case.
The vanes form structural vanes, i.e load-carrying struts. The vanes may also have aerodynamic characteristics, wherein they are designed to redirect a swirling flow from the upstream fan. Such a vane is usually denoted an integrated OGV in this application.
It is desirable to achieve a cost-efficient method for producing a vane, which results in a vane with low weight. The method should further be suited for producing a vane for an intermediate case in a turbofan engine.
A method according to an aspect of the present invention includes the steps of casting at least one of a vane leading edge part and a vane trailing edge part, and connecting the leading edge part and the trailing edge part. It has turned out that casting gives a sufficient dimensional accuracy and surface roughness for application as an edge part in a vane in an intermediate case. Especially, it creates conditions for reaching a final shape without any subsequent machining.
According to a preferred embodiment, the method comprises the step of forming the cast edge part by means of a vacuum high pressure die casting method. In this way, a low porosity is achieved, which increases the material properties and the weld ability. Further, the ductility and ultimate tensile strength is sufficiently high.
A method according to another aspect of the present invention includes the steps of forming at least one of a vane leading edge part and a vane trailing edge part with a means for attaching the vane to an external structure on opposite sides of the edge part in a longitudinal direction of the vane, forming the edge part so that it is adapted to be load carrying in a longitudinal direction of the vane and forming the vane by connecting said edge parts. Thus, each of the edge parts forms a load-carrying structure comprising the attachment means. Thus, the attachment means is integrated in the edge part, which simplifies transfer of forces between the vane and the adjacent components. Further, this design creates further conditions for a more cost-efficient production in that the different parts can be produced separately and then assembled.
According to a preferred embodiment, the method comprises the step of casting each of the leading edge part and the trailing edge part in one piece. The method further preferably comprises the step of attaching the leading edge part and the trailing edge part on opposite sides of an intermediate vane part. Thus, the final vane is assembled from three parts. The intermediate vane part is preferably formed by two plate-shaped portions at a distance from each other, which portions define opposite external surfaces of the vane. Further, the method preferably comprises the step of connecting at least one of the leading edge part and the trailing edge part to the intermediate vane part via welding.
It is also desirable to achieve a vane, which is low weight and cost-efficient in production. The vane should further be suited for application in an intermediate case in a turbofan engine.
Other advantageous embodiments of the invention and its associated advantages are apparent from the following description.